We have 3 types of salesforce collections. They are
- List
- Set
- Map
List
List is an ordered collection of elements which will allow duplicates.
Syntax
List<datatype> listName = new List<datatype>();
- The datatype allows both primitive datatypes and non-primitive datatypes
- Size of the list is dynamically increased.
Methods in List
Add
Add the values to the list.
Ex: List<String> colors =new List<String>();
colors.add(‘Red’);
colors.add(‘White’);
colors.add(‘Black’); (OR) List<String> colors =new List<String>{‘Red’,'White’,'Black’}
Get
Retrieve a values from list using index.
String getcolor = colors.get(1); —- we get the value is ‘White’ in to getcolor veriable.
Set
Replaces a former value with the value at given index.
colors.set(1,’Green’); —- List has value at index ‘ 1 ‘ is White is changed to Green.
Size
Return the number of elements in the list.
colors.size(); —- Gives the size of colors list is ’2′
Clear
Remove the elements from the list.
colors.clear();
Example: Inserting 100 contacts in contacts object
public class ContactInsertion{
list<contact> contactList = new list<contact>();
public void methodName(){
for(integer i=0; i<100 ; i++ ){
contact cont = new contact(lastname = ‘contact’ + i);
contactList .add(cont);
}
insert contactList ;
}
}
- Go through the below link for the more list methods.
Set
Set is an unordered collection of elements which will not allow duplicates.
Syntax
set<datatype> setName = new set<datatype>();
- data type allows only primitive datatypes and SObjects.
- We cannot get the retrieve the data based on index because set does not have index.
Go through the below link for the all Set methods.
Map
Map is key – value pairs.
Syntax
map<datatype,datatype> mapName = new map<datatype,datatype>();
- First datatype is key and it allows primitive datatypes and should be unique.
- Second datatype is values and it allows both primitive & non-primitive datatypes and allows duplicates.
Methods
Put()
Insert a key-value pair or replaces a value with the given value for the key .
- map.put(key,value);
Get()
Retrieves the value for a key.
- map.get(key);
keySet()
Retrieves all the keys and return type is set;
- map.keySet();
values()
Retrieves all the values and return type is list;
- map.values();
Size()
Return the number of components in the map.
- map.size();
Example: Create a map of Account Ids and Account objects.
public class AccountMapPopulation{
// Creating map with account id and account object
map <Id,Account> accountIdMap =new map<Id,Account>();
public void methodName(){
// creating the accounts
account acc1 = new account (name =’account1′ , industry = ‘ Banking’);
account acc2 =new account(name =’ account2′ , industry = ‘Agriculture’);
account acc3 = new account(name=’account3′ , industry=’Banking’);
// populating the map with account id and account object
accountIdMap .put(acc1.id,acc1);
accountIdMap .put(acc2.id,acc2);
accountIdMap .put(acc3.id,acc3);
}
}
- Go through the the below link for the more map methods.
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